This invention concerns lead-free hydrocarbon fuel compositions comprising fuel and a synergistic combination of the antiknocks: dicyclopentadienyl iron and cyclopentadienyl manganese tricarbonyl.
Dicyclopentadienyl iron compounds and substituted dicyclopentadienyl iron compounds are known to be effective in improving the octane quality of gasolines. The manner of their preparation is known in the art; see, for example, U.S. Pat. Nos. 2,680,756, 2,804,468 and 3,341,311.
Cyclopentadienyl manganese tricarbonyl compounds and substituted cyclopentadienyl manganese tricarbonyl compounds are also known to be effective octane rating improvers in gasolines. The manner of their preparation is known; see, for example, U.S. Pat. Nos. 2,818,417, 2,868,816, and 3,127,351.
Binary mixtures of antiknock compounds are known, e.g., dicyclopentadienyl iron with methylcyclopentadienyl manganese tricarbonyl; see U.S. Pat. No. 3,353,938. The patent, however, leads away from the discovery embodied in the instant invention by disclosing merely that expected octane improvement is achieved at total metal concentrations of 0.3 gram per gallon of fuel. Although accurate, the teaching does not suggest that at lower total metal concentrations, i.e., 0.05 to 0.25, there is a synergistic increase in octane rating. The patent is primarily concerned with demonstrating synergism of certain iron and nickel compounds. Particular attention is directed to column 8, lines 4 to 13 of the patent.